<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>常见的网页布局</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }

    li {
      list-style: none;
    }
    /* 只要是通栏的盒子（和浏览器一样宽）不需要指定宽度 */
    .top {
      height: 50px;
      background-color: gray;
    }

    .banner {
      width: 980px;
      height: 200px;
      background-color: gray;
      margin: 10px auto;
    }

    .box {
      width: 980px;
      height: 400px;
      /* background-color: gray; */
      margin: 0 auto;
    }

    .box ul li {
      float: left;
      width: 237px;
      height: 400px;
      background-color: gray;
      margin-right: 10px;
    }
    
    .box .last {
      margin-right: 0;
    }

    .footer {
      height: 200px;
      background-color: gray;
      margin-top: 10px;
    }
  </style>
</head>

<body>
  <div class="top"></div>
  <div class="banner"></div>
  <div class="box">
    <ul>
      <li>1</li>
      <li>2</li>
      <li>3</li>
      <li class="last">4</li>
    </ul>
  </div>
  <div class="footer"></div>
</body>

</html>